PHP Function Reference Parameter

Description

A reference is a pointer to a PHP variable.

Syntax to create reference variable

Reference variable

We have two ways to read or change the variable's contents. We can use the variable name, or you can use the reference.

Here's a simple example that creates a reference to a variable:

<?PHP/*from  w  w  w. ja  v  a  2 s.  c  om*/
         $myVar = 123; 
         $myRef = &$myVar; 
         $myRef++; 
         echo $myRef . "\n";  // Displays "124" 
         echo $myVar . "\n";  // Displays "124"   
?>

The code above generates the following result.

First a new variable, $myVar, is initialized with the value 123. Next, a reference to $myVar is created, and the reference is stored in the variable $myRef.

Note the ampersand (&) symbol after the equals sign; using this symbol creates the reference.

Because $myRef actually points to the same data. The next line of code adds one to the value of as $myVar, both $myRef and $myVar now contain the value 124.

Syntax for reference parameters

To get a function to accept an argument as a reference rather than a value, put an ampersand (&) before the parameter name within the function definition:

function myFunc(  & $aReference ){ 
  // (do stuff with $aReference) 
}   

Note

By passing a reference to a variable as an argument to a function, rather than the variable itself, you pass the argument by reference , rather than by value.

This means that the function can now alter the original value, rather than working on a copy.

Example 1

Reference parameter

<?PHP/*from w w  w .j a v a  2 s . com*/
    function resetCounter(  & $c ) { 
      $c = 0; 
    } 

    $counter = 0; 
    $counter++; 
    $counter++; 
    $counter++; 
    echo "$counter\n";  // Displays "3" 
    resetCounter( $counter ); 
    echo "$counter\n";  // Displays "0"   
?>

The code above generates the following result.